#define _CRT_SECURE_NO_WARNINGS 1

//https://leetcode.cn/problems/number-of-islands/

class Solution {
    int dx[4] = { 0, 0, 1, -1 };
    int dy[4] = { 1, -1, 0, 0 };
    bool check[301][301];
    int m, n;
    int ret = 0;
public:

    int numIslands(vector<vector<char>>& grid) {
        m = grid.size(), n = grid[0].size();
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                if (grid[i][j] == '1' && check[i][j] == false)
                {
                    ret++;
                    dfs(grid, i, j);
                }
            }
        }
        return ret;
    }

    void dfs(vector<vector<char>>& grid, int i, int j)
    {
        check[i][j] = true;
        for (int z = 0; z < 4; z++)
        {
            int x = i + dx[z], y = j + dy[z];
            if (x >= 0 && x < m && y >= 0 && y < n && !check[x][y] && grid[x][y] == '1')
            {
                dfs(grid, x, y);
            }
        }
    }
};